Liquid crystal composition and liquid crystal display device

ABSTRACT

A liquid crystal composition containing at least one compound represented by formula (1) as a first component and at least one compound selected from the group of compounds represented by formulas (2) and (3), but not containing a compound represented by formula (4), and having a negative dielectric anisotropy: 
                         
wherein R 1  is alkyl or alkenyl; R 2  is alkyl or alkoxy; R 3  is alkyl or alkoxymethyl; R 4  is alkyl; R 6  is alkyl, alkenyl or alkoxy; A 1  and A 2  are independently 1,4-cyclohexylene or 1,4-phenylene; A 3  is 1,4-cyclohexylene, 1,4-phenylene or 2-fluoro-1,4-phenylene; Z 1  is a single bond or —COO—; and n is 0 or 1.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a liquid crystal composition suitable for use in an active matrix (AM) device, and an AM device containing the composition.

2. Related Art

On a liquid crystal display device, classification based on an operating mode of liquid crystals includes phase change (PC), twisted nematic (TN), super twisted nematic (STN), optically compensated bend (OCB), in-plane switching (IPS), vertical alignment (VA), and so forth. Classification based on a driving mode includes a passive matrix (PM) and an active matrix (AM). PM is further classified into static, multiplex and so forth, and AM is classified into a thin film transistor (TFT), a metal insular metal (MIM) and so forth. TFT is further classified into amorphous silicon, polycrystal silicon and continuous grain silicon. The polycrystal silicon is classified into a high temperature type and a low temperature type according to a production process. Classification based on a light source includes a reflection type utilizing a natural light, a transmission type utilizing a backlight and a semi-transmission type utilizing both the natural light and the backlight.

These devices contain a liquid crystal composition having suitable characteristics. General characteristics of the composition should be improved to obtain an AM device having good general characteristics. Table 1 below summarizes a relationship between the general characteristics of the two. The general characteristics of the composition will be explained further based on a commercially available AM device. A temperature range of a nematic phase relates to the temperature range in which the device can be used. A desirable maximum temperature of the nematic phase is approximately 70° C. or more and a desirable minimum temperature is approximately −20° C. or less. The viscosity of the composition relates to the response time of the device. A short response time is desirable for displaying a moving image. Accordingly, a small viscosity of the composition is desirable. A small viscosity at a low temperature is more desirable.

TABLE 1 General Characteristics of a Liquid Crystal Composition and an AM Element General Characteristics of a General Characteristics No. Composition of an AM Element 1 Temperature range of a Usable temperature range is wide nematic phase is wide 2 Viscosity is small¹ Response time is short 3 Optical anisotropy is suitable Contrast ratio is large 4 Threshold voltage is low Electric power consumption is small and a contrast ratio is large 5 Specific resistance is large Voltage holding ratio is large and a contrast ratio is large Note ¹A liquid crystal composition can be injected into a cell in a short time.

The optical anisotropy of the composition relates to the contrast ratio of the device. The devices having a VA mode, an IPS mode and so forth utilize electrically controlled birefringence. A product (Δn·d) of the optical anisotropy (Δn) of the composition and the cell gap (d) of the device is designed to be a constant value to maximize the contrast ratio of the device having a VA mode, an IPS mode and so forth. An example of the value is approximately 0.30 micrometers to approximately 0.35 micrometers (VA mode) or approximately 0.20 micrometers to approximately 0.30 micrometers (IPS mode). Since the cell gap is generally approximately 3 micrometers to approximately 6 micrometers, the optical anisotropy of the composition is always in a range of approximately 0.05 to approximately 0.11. A large dielectric anisotropy of the composition contributes to a small driving voltage of the device. Accordingly, a large dielectric anisotropy is desirable. A large specific resistance of the composition contributes to a large voltage holding ratio and a large contrast ratio of the device. Accordingly, a composition having a large specific resistance is desirable at room temperature and also at a high temperature in the initial stage. A composition having a large specific resistance is desirable at room temperature and also at a high temperature after it has been used for a long time. Since an ultraviolet ray is used on production of the device, a composition having a large specific resistance is desirable at room temperature and also at a high temperature after it is irradiated with an ultraviolet ray.

A composition having a positive dielectric anisotropy is used in an AM device having a TN mode. On the other hand, a composition having a negative dielectric anisotropy is used in an AM device having a VA mode. A composition having a positive or negative dielectric anisotropy is used in an AM device having an IPS mode. A composition having a negative dielectric anisotropy is disclosed in the following patent documents: JP H8-104869 A/1996 (U.S. Pat. No. 5,599,480), JP H10-176167A/1998 (U.S. Pat. No. 5,965,060), JP H11-140447A/1999 (U.S. Pat. No. 6,066,268), JP 2000-96055 A/2000 (U.S. Pat. No. 6,676,030 B1), JP 2001-192657 A/2001 (U.S. Patent Application Publication No. 2001/0010366 A1), JP 2001-354967 A/2001 (U.S. Patent Application Publication No. 2002/0014613 A1), JP 2003-13065 A/2003 (U.S. Patent Application Publication No. 2003/0039769 A1)

SUMMARY OF THE INVENTION

The invention concerns a liquid crystal composition comprising at least one compound represented by formula (1) as a first component and at least one compound selected from the group of compounds represented by formulas (2) and (3), but not containing a compound represented by formula (4), and having a negative dielectric anisotropy:

wherein R¹ is alkyl or alkenyl; R² is alkyl or alkoxy; R³ is alkyl or alkoxymethyl; R⁴ is alkyl; R⁶ is alkyl, alkenyl or alkoxy; A¹ and A² are independently 1,4-cyclohexylene or 1,4-phenylene; A³ is 1,4-cyclohexylene, 1,4-phenylene or 2-fluoro-1,4-phenylene; Z¹ is a single bond or —COO—; and n is 0 or 1. The invention also concerns a liquid crystal crystal display device containing the composition, the use of the composition, and so forth.

DETAILED DESCRIPTION OF THE INVENTION

The terms used in the specification and claims are defined as follows:

The liquid crystal composition of the invention or the liquid crystal display device of the invention may occasionally be expressed simply as “the composition” or “the device,” respectively. A liquid crystal display device is a generic term for a liquid crystal display panel and a liquid crystal display module. Main components of the liquid crystal composition are liquid crystal compounds. The liquid crystal compound is a generic term for a compound having a liquid crystal phase such as a nematic phase at approximately 25° C., a smectic phase at approximately 25° C. and so forth, and also for a compound having no liquid crystal phase at approximately 25° C. but being useful as a component of a composition. At least one compound selected from a group of compounds represented by formula (1) may be abbreviated to “the compound (1).” At least one compound selected from the group of the compounds represented by formulas (2) and (3) may be abbreviated to “the compound (2) and the compound (3).”

In the case where the first component is a single compound, the term “the ratio of the first component” means the ratio of the compound. In the case where the first component includes two or more compounds, it means the total ratio of the compounds constituting the first component. The terms “the ratio of the second component,” “the ratio of the compound represented by formula (1-2)” and so forth are applied with the same rule.

The term “at least one compound represented by formula (1) as the first component” means that the first component is selected only from the compound (1), and also means that the first component does not contain any other compound than the compound (1) as the first component. The cases where the first component is selected from other compounds are applied with the same rule, and the case of the second component is also applied with the same rule.

The term “the compound represented by formula (1)” means, in the case where the compound (1) is a single compound, the compound itself, and in the case where the compound (1) includes two or more compounds, all of the two or more compounds (1). The other formulas are applied with the same rule.

A higher limit of a temperature range of a nematic phase may be abbreviated to “a maximum temperature.” A lower limit of a temperature range of a nematic phase may be abbreviated to “a minimum temperature.” “A specific resistance is large” means that the composition has a large specific resistance at room temperature and also at a high temperature in the initial stage, the composition has a large specific resistance at room temperature and also at a high temperature even after it has been used for a long time, and the composition has a large specific resistance at room temperature and also at a high temperature even after it is irradiated with an ultraviolet ray. “A voltage holding ratio is large” means that an device has a large voltage holding ratio at room temperature and also at a high temperature in the initial stage, the device has a large voltage holding ratio at room temperature and also at a high temperature even after it has been used for a long time, and the device has a large voltage holding ratio at room temperature and also at a high temperature even after it is irradiated with an ultraviolet ray.

In the descriptions herein, the characteristics of the composition such as the optical anisotropy and so forth are values measured in the methods disclosed in Examples. The content (percentage) of a liquid crystal compound in a composition means the percentage by weight (% by weight) based on the total weight of liquid crystal compounds.

An advantage of the invention is to provide a liquid crystal composition that satisfies many characteristics among the characteristics such as a high maximum temperature of a nematic phase, a low minimum temperature of a nematic phase, a small viscosity, a suitable optical anisotropy, a negatively large dielectric anisotropy, a small frequency dependency of a dielectric anisotropy, a small temperature dependency of a threshold voltage and a large specific resistance. One aspect of the invention is to provide a liquid crystal composition properly balanced regarding many characteristics. Another aspect of the invention is to provide a liquid crystal display device containing such a composition and having a large voltage holding ratio. A further aspect of the invention is to provide an AM device containing a composition with a minimum temperature of a nematic phase of approximately −30° C. or less, a maximum temperature of a nematic phase of approximately 100° C. or more, a small viscosity, an optical anisotropy ranging from approximately 0.05 to approximately 0.11 and a dielectric anisotropy ranging from approximately −6.5 to approximately −2.0, and being suitable for a VA mode, an IPS mode and so forth.

The invention has the following features:

1. A liquid crystal composition comprising at least one compound represented by formula (1) as a first component and at least one compound selected from the group of compounds represented by formulas (2) and (3) as a second component, but not containing a compound represented by formula (4), and having a negative dielectric anisotropy:

wherein R¹ is alkyl or alkenyl; R² is alkyl or alkoxy; R³ is alkyl or alkoxymethyl; R⁴ is alkyl; R⁶ is alkyl, alkenyl or alkoxy; A¹ and A² are independently 1,4-cyclohexylene or 1,4-phenylene; A³ is 1,4-cyclohexylene, 1,4-phenylene or 2-fluoro-1,4-phenylene; Z¹ is a single bond or —COO—; and n is 0 or 1.

2. A liquid crystal composition consisting essentially of at least one compound represented by formula (1) as a first component and at least one compound selected from the group of compounds represented by formulas (2) and (3) as a second component:

wherein R¹ is alkyl or alkenyl; R² is alkyl or alkoxy; R³ is alkyl or alkoxymethyl; R⁴ is alkyl; A¹ and A² are independently 1,4-cyclohexylene or 1,4-phenylene; A³ is 1,4-cyclohexylene, 1,4-phenylene or 2-fluoro-1,4-phenylene; Z¹ is a single bond or —COO—; and n is 0 or 1.

3. The liquid crystal composition according to item 1 or 2, wherein the first component is in a range of from approximately 35% to approximately 90% by weight, and the second component is in a range of from approximately 10% to approximately 65% by weight, based on the total weight of the liquid crystal compounds.

4. The liquid crystal composition according to item 1 or 2, wherein the composition comprises at least one compound represented by formula (2) and at least one compound represented by formula (3) as the second component.

5. The liquid crystal composition according to item 4, wherein the first component is in a range of from approximately 35% to approximately 90% by weight, the compound represented by formula (2) of the second component is in a range of from approximately 5% to approximately 35% by weight, and the compound represented by formula (3) of the second component is in a range of from approximately 5% to approximately 30% by weight, based on the total weight of the liquid crystal compounds.

6. The liquid crystal composition according to item 1 or 2, wherein the composition comprises at least one compound represented by formula (1-2) and at least one compound selected from the group of compounds represented by formulas (1-3) and (1-4) as the first component, and at least one compound selected from the group of compounds represented by formulas (2-2) and (2-3) and at least one compound represented by formula (3-1) as the second component:

wherein R⁴ and R⁵ are independently alkyl; and R⁷ is alkenyl.

7. The liquid crystal composition according to item 6, wherein the compound represented by formula (1-2) of the first component is in a range of from approximately 30% to approximately 65% by weight, the compound selected from the group of compounds represented by formulas (1-3) and (1-4) of the first component is in a range of from approximately 5% to approximately 25% by weight, the compound selected from the group of compounds represented by formulas (2-2) and (2-3) of the second component is in a range of from approximately 5% to approximately 35% by weight, and the compound represented by formula (3-1) of the second component is in a range of from approximately 5% to approximately 30% by weight, based on the total weight of the liquid crystal compounds.

8. The liquid crystal composition according to item 1 or 2, wherein the composition comprises at least one compound represented by formula (1-2) and at least one compound represented by formula (1-4) as the first component, and at least one compound selected from the group of compounds represented by formulas (2-2) and (2-3) and at least one compound represented by formula (3-1) as the second component:

wherein R⁴ and R⁵ are independently alkyl; and R⁷ is alkenyl.

9. The liquid crystal composition according to item 8, wherein the compound represented by formula (1-2) of the first component is in a range of from approximately 30% to approximately 65% by weight, the compound represented by formula (1-4) of the first component is in a range of from approximately 5% to approximately 25% by weight, the compound selected from the group of compounds represented by formulas (2-2) and (2-3) of the second component is in a range of from approximately 5% to approximately 35% by weight, and the compound represented by formula (3-1) of the second component in a range of from approximately 5% to approximately 30% by weight, based on the total weight of the liquid crystal compounds.

10. The liquid crystal composition according to item 1 or 2, wherein the composition comprises at least one compound represented by formula (1-2), at least one compound represented by formula (1-3) and at least one compound represented by formula (1-4) as the first component, and at least one compound selected from the group of compounds represented by formulas (2-2) and (2-3) and at least one compound represented by formula (3-1) as the second component:

wherein R⁴ and R⁵ are independently alkyl; and R⁷ is alkenyl.

11. The liquid crystal composition according to item 10, wherein the compound represented by formula (1-2) of the first component is in a range of from approximately 30% to approximately 65% by weight, the compound selected from the group of compounds represented by formulas (1-3) and (1-4) of the first component is in a range of from approximately 5% to approximately 25% by weight, the compound selected from the group of compounds represented by formulas (2-2) and (2-3) of the second component is in a range of from approximately 5% to approximately 35% by weight, and the compound represented by formula (3-1) of the second component is in a range of from approximately 5% to approximately 30% by weight, based on the total weight of the liquid crystal compounds.

12. The liquid crystal composition according to item 1 or 2, wherein the composition comprises at least one compound represented by formula (1-2) and at least one compound represented by formula (1-4) as the first component, and at least one compound represented by formula (2-2), at least one compound represented by formula (2-3) and at least one compound represented by formula (3-1) as the second component, and the compound represented by formula (1-2) of the first component is in a range of from approximately 30% to approximately 65% by weight, the compound represented by formula (1-4) of the first component is in a range of from approximately 5% to approximately 25% by weight, the compound selected from the group of compounds represented by formulas (2-2) and (2-3) of the second component is in a range of from approximately 5% to approximately 35% by weight, and the compound represented by formula (3-1) of the second component is in a range of from approximately 5% to approximately 30% by weight, based on the total weight of the liquid crystal compounds:

wherein R⁴ and R⁵ are independently alkyl; and R⁷ is alkenyl.

13. The liquid crystal composition according to item 1 or 2, wherein the composition comprises at least one compound represented by formula (1-2), at least one compound represented by formula (1-3) and at least one compound represented by formula (1-4) as the first component, and at least one compound represented by formula (2-2), at least one compound represented by formula (2-3) and at least one compound represented by formula (3-1) as the second component, and the compound represented by formula (1-2) of the first component is in a range of from approximately 30% to approximately 65% by weight, the compound selected from the group of compounds represented by formulas (1-3) and (1-4) of the first component is in a range of from approximately 5% to approximately 25% by weight, the compound selected from the group of compounds represented by formulas (2-2) and (2-3) of the second component is in a range of from approximately 5% to approximately 35% by weight, and the compound represented by formula (3-1) of the second component is in a range of from approximately 5% to approximately 30% by weight, based on the total weight of the liquid crystal compounds:

wherein R⁴ and R⁵ are independently alkyl; and R⁷ is alkenyl.

14. The liquid crystal composition according to one of items 1 through 13, wherein the composition further comprises an antioxidant.

15. The liquid crystal composition according to item 14, wherein the antioxidant is a compound represented by formula (7):

wherein m is an integer from 1 to 9.

16. The liquid crystal composition according to item 14 or 15, wherein the antioxidant is in a range of from approximately 50 ppm to approximately 600 ppm based on the total weight of the liquid crystal compounds.

17. A liquid display device comprising the liquid crystal composition according to one of items 1 to 16.

The invention also contains the following items: (1) The composition described above, wherein the optical anisotropy is in the range from approximately 0.05 to approximately 0.11; (2) The composition described above, wherein the maximum temperature of the nematic phase is approximately 100° C. or more and the minimum temperature of the nematic phase is approximately −30° C. or less; (3) The composition described above, which further contains an optically active compound; (4) An AM device containing the composition described above; (5) A device containing the composition described above and having the mode of IPS or VA; (6) A device of a transmission type, containing the composition described above; (7) An amorphous silicon or polycrystalline silicon TFT device, containing the composition described above; (8) Use of the composition described above as a composition having a nematic phase; and (9) Use as an optically active composition by adding an optically active compound to the composition described above.

The liquid crystal composition of the invention satisfies many characteristics among the characteristics such as a high maximum temperature of a nematic phase, a low minimum temperature of a nematic phase, a small viscosity, a suitable optical anisotropy, a negatively large dielectric anisotropy, a small frequency dependency of a dielectric anisotropy, a small temperature dependency of a threshold voltage and a large specific resistance. The composition is properly balanced regarding many characteristics. The device of the invention contains such a composition, and has a large voltage holding ratio. The device contains a composition with a minimum temperature of a nematic phase of approximately −30° C. or less, a maximum temperature of a nematic phase of approximately 100° C. or more, a small viscosity, an optical anisotropy ranging from approximately 0.05 to approximately 0.11 and a dielectric anisotropy ranging from approximately −6.5 to approximately −2.0, and is suitable for a VA mode, an IPS mode and so forth.

The composition of the invention will be explained in the following order. First, the constitution of component compounds in the composition will be explained. Second, the main characteristics of the component compounds and the main effects of the compounds on the composition will be explained. Third, a desirable ratio of the component compounds and the basis thereof will be explained. Fourth, a desirable embodiment of the component compounds will be explained. Fifth, concrete examples of the component compound will be shown. Sixth, the preparation methods of the component compound will be explained. Last, use of the composition will be explained.

First, the constitution of component compounds in the composition will be explained. The composition of the invention is classified into the composition A and the composition B. The composition A may further contain other compounds. The “other compounds” include a liquid crystal compound, an additive, an impurity, and so forth. This liquid crystal compound is different from the compounds (1) to (4). The liquid crystal compounds are mixed for the purpose of further adjusting the characteristics. The additive includes an optically active compound, a coloring matter, an antioxidant, and so forth. The optically active compound is mixed with the composition for the purpose of giving a twist angle by means of inducing a helical structure. The coloring matter is mixed with the composition to suit for the device of a guest host (GH) mode. The antioxidant is mixed with the composition in order to avoid a decrease in specific resistance caused by heating in the air, or to maintain a large voltage holding ratio at room temperature and also at a high temperature even after the device has been used for a long time. The antioxidant includes the compound represented by formula (7) and so forth. The impurity is a compound and so forth contaminated in the process such as the synthesis of a component compound and so forth.

The composition B essentially consists of the compounds selected from the compounds (1) to (3). The term “essentially” means that the composition does not contain a liquid crystal compound which is different from these compounds. The term “essentially” also means that the composition may further contain the additive, the impurity, and so forth. The components of the composition B is fewer than those of the composition A. The composition B is preferable to the composition A from the viewpoint of costs. The composition A is preferable to the composition B, because characteristics of the composition A can be further adjusted by mixing with other liquid crystal compounds.

A liquid crystal compound which is different from the compounds (1) to (4) includes a compound having a partial structure represented by formulas (5-1) to (5-5). The compound having a partial structure represented by formulas (5-1) to (5-5) increases the dielectric anisotropy positively. Such a liquid crystal compound may be mixed with a composition used for a device having a mode such as IPS and so forth. However, the compound is not proper for the composition used for a VA device. The compound having a partial structure represented by formulas (5-1) to (5-5) decreases the specific resistance and thus may be mixed with a composition used for a device having a mode such as IPS and so forth. However, the compound is not proper for the composition used for a VA device. In formulas (5-1) to (5-5), X¹ is fluorine, chlorine, cyano, —CF₃ or —OCF₃, and Y¹ and Y² are independently fluorine or chlorine. Examples of the optically active compound are represented by formulas (6-1) to (6-4).

Second, the main characteristics of the component compounds and the main effects of the compounds on the composition will be explained. The main characteristics of the component compounds are summarized in Table 2 according to the features of the invention. In Table 2, the letter L represents large or high, the letter M represents a middle degree and the letter S represents small or low. The numeral 0 (zero) indicates that a dielectric anisotropy is nearly zero (or very small).

TABLE 2 Characteristics of Compounds (1) (2) (3) Maximum Temperature S-M M L Viscosity S-M S M Optical Anisotropy S-M S-M M-L Dielectric Anisotropy M-L¹ 0 0 Specific Resistance L L L ¹negatively large

The specific feature of the composition of the invention lies in the combination of the compounds (1) to (3). The compound (1) has a large effect for increasing negatively a dielectric anisotropy of the composition. The compound (2) has a large effect for increasing a maximum temperature of the composition. The compound (3) has a further large effect for increasing a maximum temperature of the composition. Dielectric anisotropy of the typical component compounds is summarized in Table 3. Table 3 shows that a low threshold voltage for driving a device depends mainly on the compound (1). The compounds are shown according to the notation in Table 4.

TABLE 3 Dielectric Anisotropy of Compounds Desirable Representative Dielectric Component Compound Compound Anisotropy First Component (1-2) 3-HB(2F,3F)-O2 −6.0 (1-3) 2-HHB(2F,3F)-1 −3.6 (1-4) 3-HHB(2F,3F)-O2 −5.9 Second Component (2-2) V-HHB-1 0.3 (2-3) 3-HHEH-5 −0.9 Third Component (3-1) 3-HHEBH-3 −0.7 (3-3) 1O1-HBBH-5 0.1

The main effects of the component compounds on the composition will be explained. The compound (1) increases negatively a dielectric anisotropy, and increases a viscosity of the composition. The compound (1) includes the compounds (1-2) to (1-4). The compound (1-2) especially increases negatively a dielectric anisotropy, and decreases a maximum temperature of a nematic phase of the composition. The compounds (1-3) and (1-4) increase a maximum temperature of a nematic phase of the composition. The compound (1-3) decreases a minimum temperature of a nematic phase of the composition. The compound (1-4) especially increases negatively a dielectric anisotropy of the composition.

The compounds (2) and (3) decreases a viscosity, making a dielectric anisotropy close to zero, and increase a maximum temperature of the composition. The compound (2) decreases a minimum temperature of the composition. The compound (3) especially increases a maximum temperature of a nematic phase of the composition.

Third, a desirable ratio of the component compound and the basis therefor will be explained. The desirable ratio is the same in both compositions A and B. A desirable ratio of the first component is approximately 35% by weight or more for increasing negatively a dielectric anisotropy and is approximately 90% by weight or less for decreasing a viscosity. A more desirable ratio is from approximately 50% to approximately 70% by weight for further increasing negatively a dielectric anisotropy and further decreasing a viscosity. A desirable ratio of the second component is approximately 10% by weight or more for decreasing a viscosity and is approximately 65% by weight or less for increasing negatively a dielectric anisotropy. A more desirable ratio is from approximately 30% to approximately 50% by weight for further decreasing a viscosity and further increasing negatively a dielectric anisotropy.

In the case where the second component contains the compounds (2) and (3), a desirable ratio of the compound (2) is approximately 5% by weight or more for decreasing a viscosity and is from approximately 35% by weight or less for decreasing a minimum temperature. A more desirable ratio is from approximately 20% to approximately 30% by weight for further decreasing a viscosity and further decreasing a minimum temperature. A desirable ratio of the compound (3) is approximately 5% by weight or more for increasing a maximum temperature and is approximately 30% by weight or less for decreasing a minimum temperature. A more desirable ratio is from approximately 10% to approximately 20% by weight for further increasing a maximum temperature and further decreasing a minimum temperature.

In the case where the second component contains the compound (1-2) and the compound (1-3) or (1-4), a desirable ratio of the compound (1-2) is approximately 30% by weight or more for decreasing negatively a dielectric anisotropy and is approximately 65% by weight or less for increasing a maximum temperature. A more desirable ratio is from approximately 45% to approximately 55% by weight for further increasing negatively a dielectric anisotropy and further increasing a maximum temperature. A desirable ratio of the compound (1-3) and/or the compound (1-4) is approximately 5% by weight or more for increasing a maximum temperature and approximately 25% by weight or less for decreasing a minimum temperature. A more desirable ratio is from approximately 5% to approximately 15% by weight for further increasing a maximum temperature and further decreasing a minimum temperature. A further desirable ratio is from approximately 45% to approximately 55% by weight for further increasing negatively a dielectric anisotropy and further decreasing a minimum temperature of a nematic phase.

A desirable ratio of the compound (1-2), a desirable ratio of the compound (1-2-2) or a desirable ratio of a total of the compounds (1-2-1) and (1-2-2) is approximately 5% by weight or more for increasing negatively a dielectric anisotropy and is approximately 25% by weight or less for decreasing a minimum temperature of a nematic phase. A more desirable ratio is from approximately 5% to approximately 15% by weight. The upper limit of approximately 15% by weight or less is determined for further decreasing a minimum temperature of a nematic phase.

In the composition A, a desirable ratio of a total of the first component and the second component is approximately 70% by weight or more for obtaining good characteristics. A more desirable ratio is approximately 90% by weight or more.

A method of adding an antioxidant to the composition may be employed to avoid decrease in specific resistance caused by heating in the air, or for obtaining a high voltage holding ratio at room temperature and also at a high temperature even after it has been used for a long time. When an antioxidant is added to the composition, a desirable ratio is approximately 50 ppm or more for obtaining its effect. A desirable ratio is approximately 600 ppm or less for increasing a maximum temperature or decreasing a minimum temperature of the composition. A more desirable ratio is from approximately 100 ppm to approximately 300 ppm. The ratio (ppm) is based on the total weight of liquid crystal compounds.

Fourth, a desirable embodiment of the component compound will be explained. The symbol R¹ was used for many compounds in the chemical formulas for the component compounds. R¹ may be identical or different in these compounds. In one case, for example, R¹ of the compound (1) is ethyl and R¹ of the compound (2) is ethyl. In another case, R¹ of the compound (1) is ethyl and R¹ of the compound (2) is propyl. This rule is also applicable to the symbols R², A₁, Z¹, n, and so forth.

Desirable R¹ is alkyl having 1 to 10 carbons or alkenyl having 2 to 10 carbons. Desirable R² is alkyl having 1 to 10 carbons or alkoxy having 1 to 10 carbons. Desirable R³ is alkyl having 1 to 10 carbons or alkoxymethyl having 2 to 10 carbons. Desirable R⁴ and R⁵ are alkyl having 1 to 10 carbons. Desirable R⁶ is alkyl having 1 to 10 carbons, alkoxy having 1 to 10 carbons or alkenyl having 2 to 10 carbons. Desirable R⁷ and R⁸ are alkenyl having 2 to 10 carbons.

Desirable alkyl is methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, or octyl. More desirable alkyl is ethyl, propyl, butyl, pentyl, or heptyl for decreasing a viscosity.

Desirable alkoxy is methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy, or heptyloxy. More desirable alkoxy is methoxy or ethoxy for decreasing a viscosity.

Desirable alkoxymethyl is methoxymethyl, ethoxymethyl, propoxymethyl, butoxymethyl, or pentyloxymethyl. More desirable alkoxymethyl is methoxymethyl for decreasing a viscosity.

Desirable alkenyl is vinyl, 1-propenyl, 2-propenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl, 1-hexenyl, 2-hexenyl, 3-hexenyl, 4-hexenyl, or 5-hexenyl. More desirable alkenyl is vinyl, 1-propenyl, 3-butenyl, or 3-pentenyl for decreasing a viscosity. A desirable configuration of —CH═CH— in these alkenyl depends on the position of a double bond. Trans is desirable in the alkenyl such as 1-propenyl, 1-butenyl, 1-pentenyl, 1-hexenyl, 3-pentenyl, and 3-hexenyl for decreasing a viscosity. Cis is desirable in the alkenyl such as 2-butenyl, 2-pentenyl and 2-hexenyl for decreasing a viscosity.

A¹ and A² are 1,4-cyclohexylene or 1,4-phenylene. A³ is 1,4-cyclohexylene, 1,4-phenylene or 2-fluoro-1,4-phenylene. On the configuration of 1,4-cyclohexylene, trans is preferable to cis for increasing a maximum temperature. Fluorine of 2-fuluoro-1,4-phenylene is positioned on the right side or the left side of the ring. A desirable position is the right side as in the compound (3-4).

Z¹ is a single bond or —COO—. A bonding group of —COO— is positioned in the direction in the compound (2-3) or (3-1).

Fifth, concrete examples of the component compound will be shown. In the desirable compounds described below, R⁴ and R⁵ are independently alkyl having 1 to 10 carbons, and R⁷ is alkenyl having 2 to 10 carbons. More desirable alkyl or alkenyl is as described above. In these desirable compounds, trans is preferable to cis for the configuration of 1,4-cyclohexylene for increasing a maximum temperature.

Desirable compound (1) is the compounds (1-1) to (1-12). More desirable compound (1) is the compounds (1-1) to (1-6) for decreasing a production cost. Especially desirable compound (1) is the compounds (1-2) to (1-4) for especially increasing negatively a dielectric anisotropy.

Desirable compound (2) is the compounds (2-1) to (2-6). More desirable compound (2) is the compounds (2-2) to (2-4) for decreasing a viscosity. Especially desirable compound (2) is the compounds (2-2) and (2-3) for further decreasing a viscosity.

Desirable compound (3) is the compounds (3-1) to (3-4). More desirable compound (3) is the compounds (3-1), (3-3) and (3-4) for decreasing a viscosity. Especially desirable compound (3) is the compounds (3-1) for further decreasing a viscosity.

When an antioxidant is added to the composition, a desirable antioxidant is the compound (7):

wherein m is an integer from 1 to 9. Desirable m is 1, 3, 5, 7, or 9. More desirable m is 1 and 7. When m is 1, the compound has a large volatility, and is effective in preventing the decrease of specific resistance caused by heating in the air. When m is 7, the compound has a small volatility, and is effective in maintaining a large voltage holding ratio at room temperature and also at a high temperature even after the device has been used for a long time.

One of the characteristic features of the composition of the invention is that the compound (4) is not contained. When the compound (4) is mixed with the composition of the invention, the advantages of the invention cannot be obtained. The compound (4) includes the compounds (4-1) to (4-6) and so forth. In these formulas, R⁴ and R⁵ are independently alkyl, and R⁷ and R⁸ are independently alkenyl.

Sixth, the preparation methods of the component compounds will be explained. These compounds can be prepared by known methods. The preparation method will be exemplified below. The compounds (1-2) and (1-4) are prepared by the method disclosed in JP H2-503441 A/1990. The compound (2-3) is prepared by the method disclosed in JP S54-106454 A/1979. The compound (3-3) is prepared by the method disclosed in JP S58-219137 A/1983. The compound (7), wherein m is 1, is commercially available. The compound is available, for example, from Sigma-Aldrich, Inc. The compound (7), wherein m is 7, is prepared by the method disclosed in U.S. Pat. No. 3,660,505.

The compounds for which preparation methods were not described above can be prepared according to the methods described in Organic Syntheses (John Wiley & Sons, Inc.), Organic Reactions (John Wiley & Sons, Inc.), Comprehensive Organic Synthesis (Pergamon Press), New Experimental Chemistry Course (Shin Jikken Kagaku Kouza) (Maruzen, Inc.), and so forth. The composition is prepared according to known methods using the compounds thus obtained. For example, the component compounds are mixed and dissolved in each other by heating.

Last, use of the composition will be explained. Most of the compositions have a minimum temperature of approximately approximately −30° C. or less, a maximum temperature of approximately 100° C. or more, a dielectric anisotropy of −6.5 to approximately −0.2, and an optical anisotropy of approximately 0.05 to approximately 0.11. The device containing the composition has a large voltage holding ratio. The composition is suitable for an AM device. The composition is suitable especially for an AM device having a VA mode of a transmission type.

The composition having an optical anisotropy of approximately 0.05 to approximately 0.18 and further the composition having an optical anisotropy of approximately 0.05 to approximately 0.20 may be prepared by controlling ratios of the component compounds or by mixing other liquid crystal compounds. The composition can be used as a composition having a nematic phase and as an optically active composition by adding an optically active compound.

The composition can be used for an AM device. It can also be used for a PM device. The composition can also be used for an device having a mode such as PC, TN, STN, ECB, OCB, IPS, and so forth. It is desirable to use the composition for a device having a mode of VA or IPS. These devices may be of a reflection type, a transmission type or a semi-transmission type. It is desirable to use the composition for a device of a transmission type. It can be used for an amorphous silicon-TFT device or a polycrystal silicon-TFT device. The composition is also usable for a nematic curvilinear aligned phase (NCAP) device prepared by microcapsulating the composition, and for a polymer dispersed (PD) device in which a three dimensional net-work polymer is formed in the composition, for example, a polymer network (PN) device.

EXAMPLES

The invention will be explained in detail by way of Examples. The invention is not limited by the Examples described below. The compounds described in the Comparative Examples and the Examples are expressed by the symbols according to the definition in Table 4. The parenthesized number next to the symbolized compounds in the Examples corresponds to the number of the desirable compound. The symbol (−) means other liquid crystal compound. A ratio (percentage) of a liquid crystal compound is percentage by weight (% by weight) based on the total weight of liquid crystal compounds. Last, the characteristics of the composition are summarized.

TABLE 4 Method of Description of Compound using Symbols R—(A₁)—Z₁— . . . —Z_(n)—(A_(n))—X Symbol (1) Left Terminal Group R— C_(n)H_(2n+1)— n- C_(n)H_(2n+1)O— nO— C_(n)H_(2n+1)OC_(m)H_(2m)— nOm- CH₂═CH— V— CH₂═CHC_(n)H_(2n)— Vn— CF₂═CH— VFF— (2) Ring Structure —An—

B

B(2F)

B(F)

B(2F,3F)

H (3) Bonding Group —Zn— —C₂H₄— 2 —COO— E —CH₂O— 1O (4) Right Terminal Group —X —C_(n)H_(2n+1) -n —OC_(n)H_(2n+1) —On —CH═CH₂ —V —CH═CHC_(n)H_(2n+1) —Vn —Cl —CL (5) Example of Description Example 1 3-HB(2F,3F)—O2

Example 2 1O1-HBBH-5

Example 3 V—HHB-1

The composition is prepared by first measuring components such as a liquid crystal compound and then by mixing them. Thus, it is easy to calculate the percentage by weight of the component. However, it is not easy to calculate exactly the ratios of the components by analyzing the composition with gas chromatography. It is because the correction coefficient depends on the kind of a liquid crystal compound. Fortunately, the correction coefficient is approximately 1. Furthermore, the difference of approximately 1% by weight in the component compound only slightly influences on characteristics of the composition. Therefore, the peak area ratio of the component peaks in the gas chromatograph can be regarded as a percentage by weight of the component compound. Namely, the results of gas chromatographic analysis (peak area ratio) are considered to be equivalent to the percentage by weight of a liquid crystal compound without correction.

When a sample was a composition, it was measured as it was, and the obtained value is described here. When a sample was a compound, a sample for measurement was prepared by mixing 15% by weight of the compound and 85% by weight of mother liquid crystals. A value of characteristic of the compound was calculated by extrapolating from a value obtained by measurement. Namely: Extrapolated value=(value measured−0.85×value measured for mother liquid crystals)/0.15.

When a smectic phase (or crystals) separated out at this ratio at 25° C., a ratio of the compound and mother liquid crystals was changed step by step in the order of (10% by weight/90% by weight), (5% by weight/95% by weight), (1% by weight/99% by weight), respectively. Values for a maximum temperature, optical anisotropy, viscosity, and dielectric anisotropy of the compound were obtained by the extrapolation.

The composition of the mother liquid crystals is as shown below:

Measurement of the characteristics was carried out according to the following methods. Most methods are described in the Standard of Electric Industries Association of Japan, EIAJ ED-2521 A or those with some modifications. A TFT was not attached to TN and VA devices used for measurement.

A maximum temperature of a nematic phase (NI; ° C.): A sample was placed on a hot plate in a melting point apparatus equipped with a polarizing microscope and was heated at the rate of 1° C. per minute. A temperature was measured when a part of the sample began to change from a nematic phase into an isotropic liquid. A higher limit of a temperature range of a nematic phase may be abbreviated to “a maximum temperature.”

A minimum temperature of a nematic phase (Tc; ° C.): A sample having a nematic phase was put in a VA device having a distance between two glass substrates (cell gap) of 4 micrometers with an antiparallel rubbing direction, and the device was sealed with an UV curable adhesive. The device was then kept in a freezer at temperatures of 0° C., −10° C., −20° C., and −30° C. for ten days, respectively and a liquid crystal phase was observed. For example, when the sample remained in a nematic phase at −20° C. and changed to crystals or a smectic phase at −30° C., Tc was expressed as ≦−20° C. A lower limit of a temperature range of a nematic phase may be abbreviated to “a minimum temperature.”

Optical anisotropy (anisotropy refractive index Δn; measured at 25° C.): Measurement was carried out with an Abbe refractometer mounting a polarizing plate on an ocular using a light at a wavelength of 589 nanometers. The surface of a main prism was rubbed in one direction, and then a sample was dropped on the main prism. Refractive index n∥ was measured when the direction of a polarized light was parallel to that of the rubbing. Refractive index n⊥ was measured when the direction of a polarized light was perpendicular to that of the rubbing. A value of optical anisotropy was calculated from the following equation: Δn=n∥−n⊥.

Dielectric anisotropy (Δ∈; measured at 25° C.): A sample having a nematic phase was put in a VA device having a distance between two glass substrates (cell gap) of 4 micrometers with an antiparallel rubbing direction, and the device was sealed with an UV curable adhesive. Sine waves (0.5 volts, 1 kilohertz) were impressed onto the device, and a dielectric constant (∈∥) that is parallel to a liquid crystal molecule was measured after 2 seconds. A sample was put in a TN device having a distance between two glass substrate (cell gap) of 9 micrometers and a twist angle of 80°. Sine waves (0.5 volts, 1 kilohertz) were impressed onto the device, and a dielectric constant (∈⊥) that is perpendicular to a liquid crystal molecule was measured after 2 seconds. A value of a dielectric anisotropy was calculated from the following equation: Δ∈=∈∥−∈⊥.

Frequency dependency of dielectric anisotropy (Δ∈−f; measured at −20° C.): Dielectric anisotropy at −20° C. was measured by the measurement method for dielectric anisotropy described above. The frequency of the sine wave was 100 Hz and 100 kHz, and ∈∥ or ∈⊥ was measured after 6 seconds from impressing a voltage. Frequency dependency of dielectric anisotropy was a value obtained by subtracting a dielectric anisotropy measured at 100 kHz from a dielectric anisotropy measured at 100 Hz. It was determined that when the value was as close as to zero, frequency dependency of dielectric anisotropy was small, that is, the sample was excellent in frequency dependency of dielectric anisotropy. Frequency dependency of dielectric anisotropy may be abbreviated to “frequency dependency.”

Threshold voltage (Vth; measured at 25° C.; V): Measurement was carried out with LCD Evaluation System Model LCD-5100 made by Otsuka Electronics Co., Ltd. Light source is a halogen lamp. A sample was poured into a VA device of a normally black mode, in which a cell gap between two glass plates was 4 micrometers with an antiparallel rubbing direction, and the device was sealed with an UV curable adhesive. Voltage to be impressed onto the device (70 Hz, rectangular waves) was stepwise increased by 0.02 volt starting from zero volt up to 20 volts. During the stepwise increasing, a light was irradiated to the device in a perpendicular direction, and an amount of the light passing through the device was measured. Voltage-transmission curve was prepared, in which a maximum amount of a light corresponded to 100% transmittance, a minimum amount of a light corresponded to 0% transmittance. Threshold voltage is a value at 10% transmittance.

Temperature dependency of threshold voltage (Vth-T; V): Threshold voltage was measured at 20° C. and 70° C. by the measurement method for threshold voltage described above. Temperature dependency of threshold voltage was a value obtained by subtracting a threshold voltage measured at 70° C. from a threshold voltage measured at 20° C. It was determined that when the value was as close as to zero, temperature dependency of threshold voltage was small, that is, the sample was excellent in temperature dependency of threshold voltage. Temperature dependency of threshold voltage may be abbreviated to “temperature dependency.”

Voltage holding ratio (VHR; measured at 25° C. and 100° C.; %): A TN device used for measurement has a polyimide-alignment film and the cell gap between two glass plates is 4.5 micrometers. A sample was poured into the device, and then the device was sealed with an adhesive which is polymerized by the irradiation of ultraviolet light. The TN device was impressed and charged with pulse voltage (60 microseconds at 5 volts). Decreasing voltage was measured for 16.7 milliseconds with High Speed Voltmeter and the area A between a voltage curve and a horizontal axis in a unit cycle was obtained. The area B was an area without decreasing. Voltage holding ratio is a percentage of the area A to the area B. A voltage holding ratio measured and obtained at 25° C. was expressed as VHR-1. A voltage holding ratio measured and obtained at 100° C. was expressed as VHR-2. Next, this TN device was heated at 100° C. for 250 hours. Separately, this TN device was irradiated with an ultraviolet ray (UV). The irradiation condition was a ultra-high-pressure mercury lamp (USH-500D, produced by Ushio, Inc., 500 W) as an UV light source, a distance between the light source and the device of 20 cm, and an irradiation time of 20 minutes. VHR-3 is a voltage holding ratio measured and obtained at 25° C. after heating. VHR-4 is a voltage holding ratio measured and obtained at 80° C. after heating. VHR-5 is a voltage holding ratio measured and obtained at 25° C. after irradiation with UV. VHR-6 is a voltage holding ratio measured and obtained at 80° C. after irradiation with UV. VHR-1 and VHR-2 correspond to evaluation of a device at the initial stage. VHR-3 and VHR-4 correspond to evaluation of a device after it has been used for a long time. VHR-5 and VHR-6 correspond to evaluation of light stability of a device.

Response time (τ; measured at 25° C.; millisecond): Measurement was carried out with LCD Evaluation System Model LCD-5100 made by Otsuka Electronics Co., Ltd. Light source is a halogen lamp. Low-pass filter was set at 5 kilohertz. A sample was poured into a VA device of a normally black mode, in which a cell gap between two glass plates was 4 micrometers with an antiparallel rubbing direction, and the device was sealed with an UV curable adhesive. Rectangle waves (70 Hertz, a voltage where a transmission of 100% was obtained in the measurement of threshold voltage, 0.5 seconds) were impressed to the device. During impressing, a light was irradiated to the device in a perpendicular direction, and an amount of the light passing through the device was measured. A maximum amount of a light corresponds to 100% transmittance, and a minimum amount of a light corresponds to 0% transmission. Fall time (τf) is a period of time required for the change in transmittance from 100% to 0%. Response time is the fall time.

Rotation viscosity (γ1; measured at 25° C.; mPa·s): Rotation viscosity was measured according to the method disclosed in M. Imai, et al., Molecular Crystals and Liquid Crystals, vol. 259, p. 37 (1995). A sample was placed in VA device of a normally black mode, in which a cell gap between two glass plates was 4 micrometers with an antiparallel rubbing direction, and the device was sealed with an UV curable adhesive. The VA device was impressed with a voltage in a range of from 10 V to 20 V stepwise by 1 V. After a period of 0.2 second with no impress of voltage, voltage impress was repeated with only one rectangular wave (rectangular pulse of 0.2 second) and application of no voltage (2 seconds). A peak current and a peak time of a transient current generated by the voltage impress were measured. Rotation viscosity was obtained from the measured values and the calculating equation (8) disclosed in M. Imai, et al., Molecular Crystals and Liquid Crystals, vol. 259, p. 40 (1995). As the dielectric anisotropy necessary for the calculation, the value measured by the measuring method of dielectric anisotropy described above was used.

Gas chromatographic Analysis: Gas Chromatograph Model GC-14B made by Shimadzu was used for measurement. Carrier gas is helium (2 milliliters per minute). An evaporator and a detector (FID) were set up at 280° C. and 300° C., respectively. Capillary column DB-1 (length 30 meters, bore 0.32 millimeters, film thickness 0.25 micrometers) made by J&W Scientific was used for the separation of the component compound. After the column had been kept at 200° C. for 2 minutes, it was further heated to 280° C. at the rate of 5° C. per minute. A sample was prepared into an acetone solution (0.1% by weight), and 1 microliter of the solution was injected into the evaporator. Gas chromatogram obtained showed a retention time of a peak and a peak area corresponding to the component compound.

Solvents for diluting the sample may also be chloroform, hexane, and so forth. The following capillary columns may also be used for separating the component compound: HP-1 made by Agilent Technologies Inc. (length 30 meters, bore 0.32 millimeters, film thickness 0.25 micrometers), Rtx-1 made by Restek Corporation (length 30 meters, bore 0.32 millimeters, film thickness 0.25 micrometers), and BP-1 made by SGE International Pty. Ltd. (length 30 meters, bore 0.32 millimeters, film thickness 0.25 micrometers). In order to prevent compound peaks from overlapping, a capillary column CBPI-M50-025 (50 meters) made by Shimadzu Corporation may be used. An area ratio of each peak in the gas chromatogram corresponds to a ratio of the component compound. Percentage by weight of the component compound is not completely identical to an area ratio of each peak. According to the invention, however, percentage by weight of the component compound may be regarded to be identical to an area ratio of each peak, when these capillary columns are used. This is because there is no significant difference in correction efficient of component compounds.

The invention will be compared to conventional techniques as follows.

Comparative Example 1

Example 3 was chosen from the compositions disclosed in JP H8-104869 A/1996. The basis is that the composition contains the compound (1), the compound (2) and the compound (4) of the invention. The components and characteristics of the composition are as follows. The composition has a low maximum temperature, a negatively small dielectric anisotropy and a large temperature dependency of threshold voltage.

3-HB(2F,3F)-O2 10%  5-HB(2F,3F)-O2 10%  3-HHB(2F,3F)-O2 12%  5-HHB(2F,3F)-O2 13%  2-HHB(2F,3F)-1 4% 2-HHB(2F,3F)-2 4% 3-HH-4 5% 3-HH-5 5% 3-HH-O1 6% 3-HH-O3 6% 3-HB-O1 5% 3-HB-O2 5% 3-HHEH-3 5% 3-HHEH-5 5% 4-HHEH-3 5%

In Comparative Example 1: NI=92.1° C.; T_(C)≦−30° C.; Δn=0.076; Δ∈=−2.9; Vth-T=0.16 V; VHR-1=98.8%.

Comparative Example 2

Example 1 was chosen from the compositions disclosed in JP H10-176167A/1998. The basis is that the composition contains the compound (1), the compound (2) and the compound (4) of the invention, and has the highest maximum temperature. The components and characteristics of the composition are as follows. The composition has a low maximum temperature, a negatively small dielectric anisotropy and a large temperature dependency of threshold voltage.

3-HB(2F,3F)-O2 12%  5-HB(2F,3F)-O2 11%  3-HHB(2F,3F)-O2 15%  5-HHB(2F,3F)-O2 15%  3-HH-4 5% 3-HH-5 5% 3-HH-O1 6% 3-HH-O3 6% 3-HB-2 4% 3-HB-O1 4% 3-HHEH-3 5% 3-HHEH-5 6% 4-HHEH-3 6%

In Comparative Example 2: NI=91.3° C.; T_(C)≦−30° C.; Δn=0.076; Δ∈=−3.2; Vth-T=0.12 V; VHR-1=99.0%.

Comparative Example 3

Example 1 was chosen from the compositions disclosed in JP H11-140447A/1999. The basis is that the composition contains the compound (1), the compound (2) and the compound (4) of the invention. The components and characteristics of the composition are as follows. The composition has a low maximum temperature, a negatively small dielectric anisotropy and a large temperature dependency of threshold voltage.

3-HB(2F,3F)-O2 14.5%   5-HB(2F,3F)-O2 14.5%   3-HHB(2F,3F)-O2 14%  5-HHB(2F,3F)-O2 9.5%   2-HHB(2F,3F)-1 6.5%   3-HHB(2F,3F)-1 6.5%   3-HB(F)B-2 4% 5-HB(F)B-2 3.5%   3-BB(2F)B(2F)-CL 3% 5-BB(2F)B(2F)-CL 3% 5-HH-V 5% 3-HB-2 2% 3-HB-O1 2% 3-HB-O2 2% 3-HB-O4 2% 3-HBB-2 5% 5-HBB-2 3%

In Comparative Example 3: NI=84.1° C.; T_(C)≦−30° C.; Δn=0.110; Δ∈=−3.2; Vth-T=0.21 V; VHR-1=98.9%.

Comparative Example 4

Example 6 was chosen from the compositions disclosed in JP 2000-96055 A/2000. The basis is that the composition contains the compound (1), the compound (2) and the compound (4) of the invention, and has the highest maximum temperature. The components and characteristics of the composition are as follows. The composition has a low maximum temperature, a negatively small dielectric anisotropy and a large temperature dependency of threshold voltage.

5-HB(2F,3F)-O4 11%  3-HHB(2F,3F)-O2 10%  5-HHB(2F,3F)-O2 10%  2-HHB(2F,3F)-1 10%  3-HHB(2F,3F)-1 10%  3-HHEB(2F,3F)-O2 8% 3-HH-4 3% 3-HH-5 5% 3-HH-O1 11%  5-HH-O1 8% 5-HH-V 2% 5-HB-3 9% 3-HHEH-5 3%

In Comparative Example 4: NI=87.9° C.; T_(C)≦−30° C.; Δn=0.070; Δ∈=−2.2; Vth-T=0.19 V; VHR-1=99.1%.

Comparative Example 5

Example 2 was chosen from the compositions disclosed in JP 2001-192657 A/2001. The basis is that the composition contains the compound (1), the compound (2) and the compound (4) of the invention. The components and characteristics of the composition are as follows. The composition has a low maximum temperature, a negatively small dielectric anisotropy and a large temperature dependency of threshold voltage.

3-HB(2F,3F)-O4 10%  5-HB(2F,3F)-O4 10%  2-HHB(2F,3F)-O2 10%  3-HHB(2F,3F)-O2 10%  5-HHB(2F,3F)-O2 9% 2O-HHB(2F,3F)-1 6% 3O-HHB(2F,3F)-1 4% 4O-HHB(2F,3F)-1 7% 3-HH-4 6% 3-HH-5 3% 3-HH-O1 9% 5-HH-O1 7% 3-HHEH-3 3% 3-HHEH-5 3% 4-HHEH-3 3%

In Comparative Example 5: NI=92.3° C.; T_(C)≦−30° C.; Δn=0.076; Δ∈=−3.3; Vth-T=0.12 V; VHR-1=98.9%.

Comparative Example 6

Example 5 was chosen from the compositions disclosed in JP 2001-354967 A/2001. The basis is that the composition contains the compound (1), the compound (2) and the compound (4) of the invention, and has the highest maximum temperature. The components and characteristics of the composition are as follows. The composition has a low maximum temperature, a negatively small dielectric anisotropy and a large temperature dependency of threshold voltage.

3-HB(2F,3F)-O4 11% 5-HB(2F,3F)-O4 16% 3-HHB(2F,3F)-O2 11% 2-HBB(2F,3F)-O2 12% 3-HBB(2F,3F)-O2 12% 3-HH-5  5% 3-HH-V1  8% 5-HH-V 12% 3-HB-O2  6% V2-HHB-1  7%

In Comparative Example 6: NI=83.3° C.; T_(C)≦−30° C.; Δn=0.097; Δ∈=−3.1; Vth-T=0.25 V; VHR-1=99.0%.

Comparative Example 7

Example 16 was chosen from the compositions disclosed in JP 2003-13065 A/2003. The basis is that the composition contains the compound (1), the compound (2) and the compound (4) of the invention, and has the highest maximum temperature. The components and characteristics of the composition are as follows. The composition has a low maximum temperature, a negatively small dielectric anisotropy and a large temperature dependency of threshold voltage.

3-HB(2F,3F)-O4  4% 5-HB(2F,3F)-O2 12% 5-HB(2F,3F)-O4  9% 1-HHB(2F,3F)-O2 12% 2-HBB(2F,3F)-O2 13% 3-HBB(2F,3F)-O2 13% 3-HH-5  6% 3-HH-V1 11% 5-HH-V 12% 3-HH1OH-3  3% 4-HH1OH-3  3% 3-HHB-2  2%

In Comparative Example 7: NI=86.0° C.; T_(C)≦−30° C.; Δn=0.097; Δ∈=−3.2; Vth-T=0.16 V; VHR-1=98.9%.

Example 1

3-HB(2F,3F)-O2 (1-2) 25% 5-HB(2F,3F)-O2 (1-2) 25% 3-HHB(2F,3F)-O2 (1-4) 5% 5-HHB(2F,3F)-O2 (1-4) 5% V-HHB-1 (2-2) 11% 3-HHEH-3 (2-3) 5% 3-HHEH-5 (2-3) 6% 4-HHEH-3 (2-3) 6% 3-HHEBH-3 (3-1) 6% 3-HHEBH-5 (3-1) 6%

In Example 1: NI=102.2° C.; T_(C)≦−30° C.; Δn=0.087; Δ∈=−4.0; γ1=85.0 mPa·s; Vth-T=0.06 V; Δ∈−f=−1.83; VHR-1=99.2%.

Example 2

3-HB(2F,3F)-O2 (1-2) 25% 5-HB(2F,3F)-O2 (1-2) 25% 3-HHB(2F,3F)-O2 (1-4) 5% 5-HHB(2F,3F)-O2 (1-4) 5% V-HHB-1 (2-2) 8% 3-HHEH-3 (2-3) 4% 3-HHEH-5 (2-3) 4% 4-HHEH-3 (2-3) 4% 3-HHEBH-3 (3-1) 10% 3-HHEBH-5 (3-1) 10%

In Example 2: NI=111.2° C.; T_(C)≦−30° C.; Δn=0.090; Δ∈=−3.7; γ1=78.8 mPa·s; Vth-T=0.05 V; Δ∈−f=−1.16; VHR-1=99.1%.

Example 3

5-HB(2F,3F)-1 (1-1) 2% 3-HB(2F,3F)-O2 (1-2) 24% 5-HB(2F,3F)-O2 (1-2) 24% 3-HHB(2F,3F)-O2 (1-4) 3% 5-HHB(2F,3F)-O2 (1-4) 4% 3-HBB(2F,3F)-O2 (1-6) 3% V-HHB-1 (2-2) 6% 3-HHEH-3 (2-3) 5% 3-HHEH-5 (2-3) 6% 4-HHEH-3 (2-3) 6% 3-HHB-O1 (2-4) 3% 3-HHEBH-3 (3-1) 7% 3-HHEBH-5 (3-1) 7%

In Example 3: NI=104.5° C.; T_(C)≦−30° C.; Δn=0.089; Δ∈=−3.7; γ1=82.0 mPa·s; Vth-T=0.04 V; Δ∈−f=−1.10; VHR-1=99.0%.

Example 4

3-HB(2F,3F)-O2 (1-2) 23% 5-HB(2F,3F)-O2 (1-2) 24% 3-HHB(2F,3F)-O2 (1-4) 5% 5-HHB(2F,3F)-O2 (1-4) 5% V2-HB(2F,3F)-O2 (1-8) 3% V-HHB-1 (2-2) 8% 3-HHEH-3 (2-3) 4% 3-HHEH-5 (2-3) 5% 4-HHEH-3 (2-3) 5% 5-HBB-2 (2-5) 4% 3-HHEBH-3 (3-1) 4% 3-HHEBH-5 (3-1) 4% 1O1-HBBH-5 (3-3) 3% 3-HB(F)BH-3 (3-4) 3%

In Example 4: NI=101.1° C.; T_(C)≦−30° C.; Δn=0.096; Δ∈=−3.7; γ1=86.5 mPa·s; Vth-T=0.05 V; Δ∈−f=−1.61; VHR-1=99.0%.

Example 5

3-HB(2F,3F)-O2 (1-2) 25% 5-HB(2F,3F)-O2 (1-2) 25% 3-HHB(2F,3F)-O2 (1-4) 5% 5-HHB(2F,3F)-O2 (1-4) 5% V-HHB-1 (2-2) 11% 3-HHEH-3 (2-3) 5% 3-HHEH-5 (2-3) 5% 4-HHEH-3 (2-3) 5% 3-HHEBH-3 (3-1) 6% 3-HHEBH-5 (3-1) 6% VFF-HHB-1 (—)  2%

In Example 5: NI=102.1° C.; T_(C)≦−30° C.; Δn=0.088; Δ∈=−3.7; γ1=86.0 mPa·s; Vth-T=0.06 V; Δ∈−f=−1.83; VHR-1=98.9%.

Example 6

3-HB(2F,3F)-O2 (1-2) 25% 5-HB(2F,3F)-O2 (1-2) 25% 3-HHB(2F,3F)-1 (1-3) 2% 3-HHB(2F,3F)-O2 (1-4) 4% 5-HHB(2F,3F)-O2 (1-4) 4% V-HHB-1 (2-2) 11% 3-HHEH-3 (2-3) 5% 3-HHEH-5 (2-3) 6% 4-HHEH-3 (2-3) 6% 3-HHEBH-3 (3-1) 6% 3-HHEBH-5 (3-1) 6%

In Example 6: NI=101.5° C.; T_(C)≦−30° C.; Δn=0.087; Δ∈=−3.9; γ1=84.3 mPa·s; Vth-T=0.06 V; Δ∈−f=−1.77; VHR-1=99.0%.

Example 7

3-HB(2F,3F)-O2 (1-2) 25% 5-HB(2F,3F)-O2 (1-2) 25% 3-HHB(2F,3F)-O2 (1-4) 5% 5-HHB(2F,3F)-O2 (1-4) 5% V-HHB-1 (2-2) 6% 3-HHEH-3 (2-3) 4% 3-HHEH-5 (2-3) 5% 4-HHEH-3 (2-3) 5% 3-HHB-O1 (2-4) 2% 5-HBB-2 (2-5) 4% 3-HHEBH-3 (3-1) 4% 3-HHEBH-5 (3-1) 4% 1O1-HBBH-5 (3-3) 3% 3-HB(F)BH-3 (3-4) 3%

In Example 7: NI=101.9° C.; T_(C)≦−30° C.; Δn=0.096; Δ∈=−3.6; γ1=86.7 mPa·s; Vth-T=0.04 V; Δ∈−f=−1.55; VHR-1=99.1%.

Example 8

3-HB(2F,3F)-O2 (1-2) 25% 5-HB(2F,3F)-O2 (1-2) 25% 3-HHB(2F,3F)-O2 (1-4) 5% 5-HHB(2F,3F)-O2 (1-4) 5% V-HHB-1 (2-2) 11% 3-HHEH-3 (2-3) 5% 3-HHEH-5 (2-3) 6% 4-HHEH-3 (2-3) 6% 3-HHEBH-3 (3-1) 6% 3-HHEBH-5 (3-1) 6%

An antioxidant of the compound (7) wherein m is 1 was added in an amount of 300 ppm to the above composition. The composition had the following characteristics. In Example 8: NI=102.2° C.; T_(C)≦−30° C.; Δn=0.087; Δ∈=−4.0; γ1=85.0 mPa·s; Vth-T=0.06 V; Δ∈−f=−1.83; VHR-1=99.2%.

Example 9

3-HB(2F,3F)-O2 (1-2) 25% 5-HB(2F,3F)-O2 (1-2) 25% 3-HHB(2F,3F)-O2 (1-4) 5% 5-HHB(2F,3F)-O2 (1-4) 5% V-HHB-1 (2-2) 8% 3-HHEH-3 (2-3) 5% 3-HHEH-5 (2-3) 4% 4-HHEH-3 (2-3) 4% 3-HHEBH-3 (3-1) 10% 3-HHEBH-5 (3-1) 10%

An antioxidant of the compound (7) wherein m is 7 was added in an amount of 200 ppm to the above composition. The composition had the following characteristics. In Example 9: NI=111.2° C.; T_(C)≦−30° C.; Δn=0.090; Δ∈=−3.7; γ1=78.80 mPa·s; Vth-T=0.05 V; Δ∈−f=−1.16; VHR-1=99.1%. 

1. A liquid crystal composition comprising at least one compound represented by formula (1) as a first component and at least one compound selected from each group of compounds represented by formulas (2) and (3) as a second component, but not containing a compound represented by formula (4), and having a negative dielectric anisotropy:

wherein R¹ is alkyl or alkenyl; R² is alkyl or alkoxy; R³ is alkyl or alkoxymethyl; R⁴ is alkyl; R⁶ is alkyl, alkenyl or alkoxy; A¹ and A² are independently 1,4-cyclohexylene or 1,4-phenylene; A³ is 1,4-cyclohexylene, 1,4-phenylene or 2-fluoro-1,4-phenylene; Z¹ is a single bond or —COO—; and n is 0 or
 1. 2. A liquid crystal composition consisting essentially of at least one compound represented by formula (1) as a first component and at least one compound selected from the group of compounds represented by formulas (2) and (3) as a second component:

wherein R¹ is alkyl or alkenyl; R² is alkyl or alkoxy; R³ is alkyl or alkoxymethyl; R⁴ is alkyl; A¹ and A² are independently 1,4-cyclohexylene or 1,4-phenylene; A³ is 1,4-cyclohexylene, 1,4-phenylene or 2-fluoro-1,4-phenylene; Z¹ is a single bond or —COO—; and n is 0 or
 1. 3. The liquid crystal composition according to claim 1, wherein the first component is in a range of from approximately 35% to approximately 90% by weight, and the second component is in a range of from approximately 10% to approximately 65% by weight, based on the total weight of the liquid crystal compounds.
 4. The liquid crystal composition according to claim 2, wherein the first component is in a range of from approximately 35% to approximately 90% by weight, and the second component is in a range of from approximately 10% to approximately 65% by weight, based on the total weight of the liquid crystal compounds.
 5. The liquid crystal composition according to claim 2, wherein the composition comprises at least one compound represented by formula (2) and at least one compound represented by formula (3) as the second component.
 6. The liquid crystal composition according to claim 5, wherein the first component is in a range of from approximately 35% to approximately 90% by weight, the compound represented by formula (2) of the second component is in a range of from approximately 5% to approximately 35% by weight, and the compound represented by formula (3) of the second component is in a range of from approximately 5% to approximately 30% by weight, based on the total weight of the liquid crystal compounds.
 7. The liquid crystal composition according to claim 5, wherein the first component is in a range of from approximately 35% to approximately 90% by weight, the compound represented by formula (2) of the second component is in a range of from approximately 5% to approximately 35% by weight, and the compound represented by formula (3) of the second component is in a range of from approximately 5% to approximately 30% by weight, based on the total weight of the liquid crystal compounds.
 8. The liquid crystal composition according to claim 1, wherein the composition comprises at least one compound represented by formula (1-2) and at least one compound selected from the group of compounds represented by formulas (1-3) and (1-4) as the first component, and at least one compound selected from the group of compounds represented by formulas (2-2) and (2-3) and at least one compound represented by formula (3-1) as the second component:

wherein R⁴ and R⁵ are independently alkyl; and R⁷ is alkenyl.
 9. The liquid crystal composition according to claim 2, wherein the composition comprises at least one compound represented by formula (1-2) and at least one compound selected from the group of compounds represented by formulas (1-3) and (1-4) as the first component, and at least one compound selected from the group of compounds represented by formulas (2-2) and (2-3) and at least one compound represented by formula (3-1) as the second component:

wherein R⁴ and R⁵ are independently alkyl; and R⁷ is alkenyl.
 10. The liquid crystal composition according to claim 8, wherein the compound represented by formula (1-2) of the first component is in a range of from approximately 30% to approximately 65% by weight, the compound selected from the group of compounds represented by formulas (1-3) and (1-4) of the first component is in a range of from approximately 5% to approximately 25% by weight, the compound selected from the group of compounds represented by formulas (2-2) and (2-3) of the second component is in a range of from approximately 5% to approximately 35% by weight, and the compound represented by formula (3-1) of the second component is in a range of from approximately 5% to approximately 30% by weight, based on the total weight of the liquid crystal compounds.
 11. The liquid crystal composition according to claim 9, wherein the compound represented by formula (1-2) of the first component is in a range of from approximately 30% to approximately 65% by weight, the compound selected from the group of compounds represented by formulas (1-3) and (1-4) of the first component is in a range of from approximately 5% to approximately 25% by weight, the compound selected from the group of compounds represented by formulas (2-2) and (2-3) of the second component is in a range of from approximately 5% to approximately 35% by weight, and the compound represented by formula (3-1) of the second component is in a range of from approximately 5% to approximately 30% by weight, based on the total weight of the liquid crystal compounds.
 12. The liquid crystal composition according to claim 1, wherein the composition comprises at least one compound represented by formula (1-2) and at least one compound represented by formula (1-4) as the first component, and at least one compound selected from the group of compounds represented by formulas (2-2) and (2-3) and at least one compound represented by formula (3-1) as the second component:

wherein R⁴ and R⁵ are independently alkyl; and R⁷ is alkenyl.
 13. The liquid crystal composition according to claim 2, wherein the composition comprises at least one compound represented by formula (1-2) and at least one compound represented by formula (1-4) as the first component, and at least one compound selected from the group of compounds represented by formulas (2-2) and (2-3) and at least one compound represented by formula (3-1) as the second component:

wherein R⁴ and R⁵ are independently alkyl; and R⁷ is alkenyl.
 14. The liquid crystal composition according to claim 12, wherein the compound represented by formula (1-2) of the first component is in a range of from approximately 30% to approximately 65% by weight, the compound represented by formula (1-4) of the first component is in a range of from approximately 5% to approximately 25% by weight, the compound selected from the group of compounds represented by formulas (2-2) and (2-3) of the second component is in a range of from approximately 5% to approximately 35% by weight, and the compound represented by formula (3-1) of the second component in a range of from approximately 5% to approximately 30% by weight, based on the total weight of the liquid crystal compounds.
 15. The liquid crystal composition according to claim 13, wherein the compound represented by formula (1-2) of the first component is in a range of from approximately 30% to approximately 65% by weight, the compound represented by formula (1-4) of the first component is in a range of from approximately 5% to approximately 25% by weight, the compound selected from the group of compounds represented by formulas (2-2) and (2-3) of the second component is in a range of from approximately 5% to approximately 35% by weight, and the compound represented by formula (3-1) of the second component in a range of from approximately 5% to approximately 30% by weight, based on the total weight of the liquid crystal compounds.
 16. The liquid crystal composition according to claim 1, wherein the composition comprises at least one compound represented by formula (1-2), at least one compound represented by formula (1-3) and at least one compound represented by formula (1-4) as the first component, and at least one compound selected from the group of compounds represented by formulas (2-2) and (2-3) and at least one compound represented by formula (3-1) as the second component:

wherein R⁴ and R⁵ are independently alkyl; and R⁷ is alkenyl.
 17. The liquid crystal composition according to claim 2, wherein the composition comprises at least one compound represented by formula (1-2), at least one compound represented by formula (1-3) and at least one compound represented by formula (1-4) as the first component, and at least one compound selected from the group of compounds represented by formulas (2-2) and (2-3) and at least one compound represented by formula (3-1) as the second component:

wherein R⁴ and R⁵ are independently alkyl; and R⁷ is alkenyl.
 18. The liquid crystal composition according to claim 16, wherein the compound represented by formula (1-2) of the first component is in a range of from approximately 30% to approximately 65% by weight, the compound selected from the group of compounds represented by formulas (1-3) and (1-4) of the first component is in a range of from approximately 5% to approximately 25% by weight, the compound selected from the group of compounds represented by formulas (2-2) and (2-3) of the second component is in a range of from approximately 5% to approximately 35% by weight, and the compound represented by formula (3-1) of the second component is in a range of from approximately 5% to approximately 30% by weight, based on the total weight of the liquid crystal compounds.
 19. The liquid crystal composition according to claim 17, wherein the compound represented by formula (1-2) of the first component is in a range of from approximately 30% to approximately 65% by weight, the compound selected from the group of compounds represented by formulas (1-3) and (1-4) of the first component is in a range of from approximately 5% to approximately 25% by weight, the compound selected from the group of compounds represented by formulas (2-2) and (2-3) of the second component is in a range of from approximately 5% to approximately 35% by weight, and the compound represented by formula (3-1) of the second component is in a range of from approximately 5% to approximately 30% by weight, based on the total weight of the liquid crystal compounds.
 20. The liquid crystal composition according to claim 1, wherein the composition comprises at least one compound represented by formula (1-2) and at least one compound represented by formula (1-4) as the first component, and at least one compound represented by formula (2-2), at least one compound represented by formula (2-3) and at least one compound represented by formula (3-1) as the second component, and the compound represented by formula (1-2) of the first component is in a range of from approximately 30% to approximately 65% by weight, the compound represented by formula (1-4) of the first component is in a range of from approximately 5% to approximately 25% by weight, the compound selected from the group of compounds represented by formulas (2-2) and (2-3) of the second component is in a range of from approximately 5% to approximately 35% by weight, and the compound represented by formula (3-1) of the second component is in a range of from approximately 5% to approximately 30% by weight, based on the total weight of the liquid crystal compounds:

wherein R⁴ and R⁵ are independently alkyl; and R⁷ is alkenyl.
 21. The liquid crystal composition according to claim 2, wherein the composition comprises at least one compound represented by formula (1-2) and at least one compound represented by formula (1-4) as the first component, and at least one compound represented by formula (2-2), at least one compound represented by formula (2-3) and at least one compound represented by formula (3-1) as the second component, and the compound represented by formula (1-2) of the first component is in a range of from approximately 30% to approximately 65% by weight, the compound represented by formula (1-4) of the first component is in a range of from approximately 5% to approximately 25% by weight, the compound selected from the group of compounds represented by formulas (2-2) and (2-3) of the second component is in a range of from approximately 5% to approximately 35% by weight, and the compound represented by formula (3-1) of the second component is in a range of from approximately 5% to approximately 30% by weight, based on the total weight of the liquid crystal compounds:

wherein R⁴ and R⁵ are independently alkyl; and R⁷ is alkenyl.
 22. The liquid crystal composition according to claim 1, wherein the composition comprises at least one compound represented by formula (1-2), at least one compound represented by formula (1-3) and at least one compound represented by formula (1-4) as the first component, and at least one compound represented by formula (2-2), at least one compound represented by formula (2-3) and at least one compound represented by formula (3-1) as the second component, and the compound represented by formula (1-2) of the first component is in a range of from approximately 30% to approximately 65% by weight, the compound selected from the group of compounds represented by formulas (1-3) and (1-4) of the first component is in a range of from approximately 5% to approximately 25% by weight, the compound selected from the group of compounds represented by formulas (2-2) and (2-3) of the second component is in a range of from approximately 5% to approximately 35% by weight, and the compound represented by formula (3-1) of the second component is in a range of from approximately 5% to approximately 30% by weight, based on the total weight of the liquid crystal compounds:

wherein R⁴ and R⁵ are independently alkyl; and R⁷ is alkenyl.
 23. The liquid crystal composition according to claim 2, wherein the composition comprises at least one compound represented by formula (1-2), at least one compound represented by formula (1-3) and at least one compound represented by formula (1-4) as the first component, and at least one compound represented by formula (2-2), at least one compound represented by formula (2-3) and at least one compound represented by formula (3-1) as the second component, and the compound represented by formula (1-2) of the first component is in a range of from approximately 30% to approximately 65% by weight, the compound selected from the group of compounds represented by formulas (1-3) and (1-4) of the first component is in a range of from approximately 5% to approximately 25% by weight, the compound selected from the group of compounds represented by formulas (2-2) and (2-3) of the second component is in a range of from approximately 5% to approximately 35% by weight, and the compound represented by formula (3-1) of the second component is in a range of from approximately 5% to approximately 30% by weight, based on the total weight of the liquid crystal compounds:

wherein R⁴ and R⁵ are independently alkyl; and R⁷ is alkenyl.
 24. The liquid crystal composition according to claim 1, wherein the composition further comprises an antioxidant.
 25. The liquid crystal composition according to claim 2, wherein the composition further comprises an antioxidant.
 26. The liquid crystal composition according to claim 22, wherein the composition further comprises an antioxidant.
 27. The liquid crystal composition according to claim 23, wherein the composition further comprises an antioxidant.
 28. The liquid crystal composition according to claim 24, wherein the antioxidant is a compound represented by formula (7):

wherein m is an integer from 1 to
 9. 29. The liquid crystal composition according to claim 25, wherein the antioxidant is a compound represented by formula (7):

wherein m is an integer from 1 to
 9. 30. The liquid crystal composition according to claim 26, wherein the antioxidant is a compound represented by formula (7):

wherein m is an integer from 1 to
 9. 31. The liquid crystal composition according to claim 27, wherein the antioxidant is a compound represented by formula (7):

wherein m is an integer from 1 to
 9. 32. The liquid crystal composition according to claim 24, wherein the antioxidant is in a range of from approximately 50 ppm to approximately 600 ppm based on the total weight of the liquid crystal compounds.
 33. The liquid crystal composition according to claim 25, wherein the antioxidant is in a range of from approximately 50 ppm to approximately 600 ppm based on the total weight of the liquid crystal compounds.
 34. The liquid crystal composition according to claim 26, wherein the antioxidant is in a range of from approximately 50 ppm to approximately 600 ppm based on the total weight of the liquid crystal compounds.
 35. The liquid crystal composition according to claim 27, wherein the antioxidant is in a range of from approximately 50 ppm to approximately 600 ppm based on the total weight of the liquid crystal compounds.
 36. The liquid crystal composition according to claim 28, wherein the antioxidant is in a range of from approximately 50 ppm to approximately 600 ppm based on the total weight of the liquid crystal compounds.
 37. A liquid display device comprising the liquid crystal composition according to claim
 1. 38. A liquid display device comprising the liquid crystal composition according to claim
 2. 39. A liquid display device comprising the liquid crystal composition according to claim
 22. 40. A liquid display device comprising the liquid crystal composition according to claim
 23. 41. A liquid crystal composition comprising at least one compound represented by formula (1) as a first component and at least one compound represented by formula (3) as a second component, but not containing a compound represented by formula (4), and having a negative dielectric anisotropy:

wherein R¹ alkyl or alkenyl; R² alkyl or alkoxy; R³ is alkyl or alkoxymethyl; R⁴ is alkyl; R⁶ is alkyl, alkenyl or alkoxy; A¹ and A² are independently 1,4-cyclohexylene or 1,4-phenylene; A³ is 1,4-cyclohexylene, 1,4-phenylene or 2-flouro-1,4-phenylene; Z¹ is a single bond or —COO—; and n is 0 or
 1. 